I have an Alpine gas fireplace that is about 10 years old. It has worked fine but lately when I set the thermostat to light it wil just sit. I can see the glass fogging up from the gas and then all of a sudden it will light with a big puff and flare-up. The pilot looks to be normal and stays lit through the whole thing. I feel it is dangerous as it is. and am wondering if it could be something simple that I can do myself to fix. Does anyone have some advice? I have turned off the unit until I can get it to light normally.